Set up iCloud in Mail

Question

When I try to set up my iCoud account as an email account in Apple Mail, the application fills in all the details except for my iCoud email address and password.  In the incoming mail server field, it fills in p08-imap.mail.me.com
But when I try to save the account settings, by navigating to another email account, I get the message 'Incoming mail server cannot be blank'. Yet this field cannot be typed-into. Because it is iCloud, it seems, Apple Mail makes that field read-only.
What do I do now?

Answer 1

Well, for the moment, all is well, but I am not sure why.  I un-marked Mail in iCloud prefs, and when I marked it again, the panel said it had to be done in my mail program.  (Why it's this way sometimes, and the other way sometimes remains a mystery.)
Then I went to Mail and set up an iCloud account, changing as little as possible.  For example, before, I had used [email protected] as my email addrss, but this time, I used [email protected], just because some little tea leaves said that was better. And i eschewed changing the deafult mailbox behaviors, whereas before, I had made it keep trash forever.
So this time it worked!
In the past, when I have had an iCloud account set up in Mail, the connection to the outgoing iCloud mail server would fail for no known reason, as confirmed by Connection Doctor.  But now, (AS LONG AS I TOUCH NOTHING), it seems to be OK.
One additional mystery:  though my iCloud account shows that it uses the iCloud server for outgoing mail, none of my other accounts can use it for outgoing mail, because it doesn't show up in the list of servers. Is that docmented or explained anywhere?
I will keep this inquiry open for a few days, in case something else goes South.